The Influence of Mass Configurations on Bandwidth in Velocity Amplified Vibrational Energy Harvesters

2015 ◽  
Author(s):  
Declan O’Donoghue ◽  
Ronan Frizzell ◽  
Jeff Punch
Keyword(s):  
Degrees Of Freedom ◽  
Vibrational Energy ◽  
Mass Ratio ◽  
Low Frequencies ◽  
Energy Harvesters ◽  
Mass Ratios ◽  
Electromagnetic Generators ◽  
Electromagnetic Generator ◽  
Half Power ◽  
Reduced Scale

Vibrational energy harvesters offer an alternative to batteries for the autonomous powering of low power electronic devices, such as wireless sensors. Velocity amplified electromagnetic generators (VAEGs) utilise the velocity amplification effect in order to increase the output power and operational bandwidth of an electromagnetic generator, compared to linear resonators. This effect is achieved through sequential collisions in a system of free-moving masses. The velocity amplification achieved is controlled by the number of masses or degrees-of-freedom (dofs) and the mass ratio between them. An experimental investigation into the influence of mass ratio and number of dofs on the operational bandwidth of a VAEG at low frequencies (< 30 Hz) is presented herein. VAEG systems with 2-, 3- and 4-dofs are analysed for mass ratios in the range of 3:1 to 20:1 under sinusoidal forced excitation. It is shown that 3- and 4-dof configurations offer broader bandwidths than 2-dof configurations, particularly at higher mass ratios. At lower mass ratios, the bandwidths of the 3- and 4-dof configurations decrease, while the bandwidth of the 2-dof configuration increases. At a mass ratio of 3:1, the bandwidth of the 2-dof configuration approaches that of the 3- and 4-dof configurations. The highest half-power bandwidth of 9.3 Hz was achieved by the 3-dof mass ratio 20:1 system, at an acceleration of 1 g. The total voltage harvested over the frequency range 7–30 Hz is at a maximum at a mass ratio of 5:1 for the 3- and 4-dof configurations, and at 3:1 for the 2-dof configuration. The findings of this investigation will be significant in the development of future reduced scale VAEGs.

scholarly journals A Micromachined Coupled-Cantilever for Piezoelectric Energy Harvesters

2018 ◽  
Author(s):  
Agin Vyas ◽  
L. G. H. Staaf ◽  
Cristina Rusu ◽  
Thorbjörn Ebefors ◽  
Jessica Liljeholm ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Mechanical Response ◽  
Vibrational Energy ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
Dual Resonance ◽  
Self Powered ◽  
Micro Cantilever

This paper presents a demonstration of the feasibility of fabricating micro-cantilever harvesters with extended stress distribution and enhanced bandwidth by exploiting an M-shaped two-degrees-of-freedom design. The measured mechanical response of the fabricated device displays the predicted dual resonance peak behavior with the fundamental peak at the intended frequency. This design has the features of high energy conversion efficiency in a miniaturized environment where the available vibrational energy varies in frequency. It makes such a design suitable for future large volume production of integrated self powered sensors nodes for the Internet-of-Things.

scholarly journals High-performance magneto-rheological clutches for direct-drive actuation: Design and development

2021 ◽  
pp. 1045389X2110069
Author(s):  
Sergey Pisetskiy ◽  
Mehrdad Kermani
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Dynamic Range ◽  
Complete Analysis ◽  
Mass Ratio ◽  
Direct Drive ◽  
Element Analysis ◽  
Prototype Development ◽  
Magneto Rheological ◽  
Hall Sensors

This paper presents an improved design, complete analysis, and prototype development of high torque-to-mass ratio Magneto-Rheological (MR) clutches. The proposed MR clutches are intended as the main actuation mechanism of a robotic manipulator with five degrees of freedom. Multiple steps to increase the toque-to-mass ratio of the clutch are evaluated and implemented in one design. First, we focus on the Hall sensors’ configuration. Our proposed MR clutches feature embedded Hall sensors for the indirect torque measurement. A new arrangement of the sensors with no effect on the magnetic reluctance of the clutch is presented. Second, we improve the magnetization of the MR clutch. We utilize a new hybrid design that features a combination of an electromagnetic coil and a permanent magnet for improved torque-to-mass ratio. Third, the gap size reduction in the hybrid MR clutch is introduced and the effect of such reduction on maximum torque and the dynamic range of MR clutch is investigated. Finally, the design for a pair of MR clutches with a shared magnetic core for antagonistic actuation of the robot joint is presented and experimentally validated. The details of each approach are discussed and the results of the finite element analysis are used to highlight the required engineering steps and to demonstrate the improvements achieved. Using the proposed design, several prototypes of the MR clutch with various torque capacities ranging from 15 to 200 N·m are developed, assembled, and tested. The experimental results demonstrate the performance of the proposed design and validate the accuracy of the analysis used for the development.

The Numerical Simulation of Two-Degrees-of-Freedom Vortex-Induced Vibrations of Circular Cylinder with High Mass-Ratio

2013 ◽  
Vol 284-287 ◽  
pp. 557-561
Author(s):  
Jie Li Fan ◽  
Wei Ping Huang
Keyword(s):  
Circular Cylinder ◽  
Drag Force ◽  
Frequency Ratio ◽  
Lift Force ◽  
Degrees Of Freedom ◽  
Cross Flow ◽  
High Mass ◽  
Mass Ratio ◽  
Main Frequency ◽  
Line Amplitude

The two-degrees-of-freedom VIV of the circular cylinder with high mass-ratio is numerically simulated with the software ANSYS/CFX. The VIV characteristic is analyzed in the different conditions (Ur=3, 5, 6, 8, 10). When Ur is 5, 6, 8 and 10, the conclusion which is different from the cylinder with low mass-ratio can be obtained. When Ur is 3, the frequency of in-line VIV is twice of that of cross-flow VIV which is equal to the frequency ratio between drag force and lift force, and the in-line amplitude is much smaller than the cross-flow amplitude. The motion trace is the crescent. When Ur is 5 and 6, the frequency ratio between the drag force and lift force is still 2, but the main frequency of in-line VIV is mainly the same as that of cross-flow VIV and the secondary frequency of in-line VIV is equal to the frequency of the drag force. The in-line amplitude is still very small compared with the cross-flow amplitude. When Ur is up to 8 and 10, the frequency of in-line VIV is the same as the main frequency of cross-flow VIV which is close to the inherent frequency of the cylinder and is different from the frequency of drag force or lift force. But the secondary frequency of cross-flow VIV is equal to the frequency of the lift force. The amplitude ratio of the VIV between in-line and cross-flow direction is about 0.5. When Ur is 5, 6, 8 and 10, the motion trace is mainly the oval.

scholarly journals Wafer Level Fabrication of Vibrational Energy Harvesters using Bulk PZT Sheets

2012 ◽  
Vol 47 ◽  
pp. 1041-1044 ◽  
Author(s):  
P. Janphuang ◽  
R. Lockhart ◽  
D. Briand ◽  
N.F. de Rooij
Keyword(s):  
Vibrational Energy ◽  
Wafer Level ◽  
Energy Harvesters

scholarly journals Two Contact Binaries with Mass Ratios Close to the Minimum Mass Ratio

2021 ◽  
Vol 922 (2) ◽  
pp. 122
Author(s):  
Kai Li ◽  
Qi-Qi Xia ◽  
Chun-Hwey Kim ◽  
Shao-Ming Hu ◽  
Di-Fu Guo ◽  
...  
Keyword(s):  
Gyration Radius ◽  
Mass Ratio ◽  
Mass Ratios ◽  
Contact Binaries ◽  
Contact Binary ◽  
Low Mass ◽  
Ratio Limit ◽  
Low Mass Ratio ◽  
Diagram Analysis

Abstract The cutoff mass ratio is under debate for contact binaries. In this paper, we present the investigation of two contact binaries with mass ratios close to the low mass ratio limit. It is found that the mass ratios of VSX J082700.8+462850 (hereafter J082700) and 1SWASP J132829.37+555246.1 (hereafter J132829) are both less than 0.1 (q ∼ 0.055 for J082700 and q ∼ 0.089 for J132829). J082700 is a shallow contact binary with a contact degree of ∼19%, and J132829 is a deep contact system with a fill-out factor of ∼70%. The O − C diagram analysis indicated that the two systems manifested long-term period decreases. In addition, J082700 exhibits a cyclic modulation which is more likely resulting from the Applegate mechanism. In order to explore the properties of extremely low mass ratio contact binaries (ELMRCBs), we carried out a statistical analysis on contact binaries with mass ratios of q ≲ 0.1 and discovered that the values of J spin/J orb of three systems are greater than 1/3. Two possible explanations can interpret this phenomenon. One explanation is that some physical processes, unknown to date, are not considered when Hut presented the dynamic stability criterion. The other explanation is that the dimensionless gyration radius (k) should be smaller than the value we used (k 2 = 0.06). We also found that the formation of ELMRCBs possibly has two channels. The study of evolutionary states of ELMRCBs reveals that their evolutionary states are similar with those of normal W UMa contact binaries.

Transient Response of MDOF Systems With Inerters to Nonstationary Stochastic Excitation

2017 ◽  
Vol 84 (10) ◽  
Author(s):  
Sami F. Masri ◽  
John P. Caffrey ◽  
Hui Li
Keyword(s):  
Degrees Of Freedom ◽  
Broad Band ◽  
Primary System ◽  
Mean Square ◽  
Stochastic Excitation ◽  
Mass Ratio ◽  
Tuning Parameters ◽  
Mdof Systems ◽  
Mean Square Response ◽  
Arbitrary Location

Explicit, closed-form, exact analytical expressions are derived for the covariance kernels of a multi degrees-of-freedom (MDOF) system with arbitrary amounts of viscous damping (not necessarily proportional-type), that is equipped with one or more auxiliary mass damper-inerters placed at arbitrary location(s) within the system. The “inerter” is a device that imparts additional inertia to the vibration damper, hence magnifying its effectiveness without a significant damper mass addition. The MDOF system is subjected to nonstationary stochastic excitation consisting of modulated white noise. Results of the analysis are used to determine the dependence of the time-varying mean-square response of the primary MDOF system on the key system parameters such as primary system damping, auxiliary damper mass ratio, location of the damper-inerter, inerter mass ratio, inerter node choices, tuning of the coupling between the damper-inerter and the primary system, and the excitation envelope function. Results of the analysis are used to determine the dependence of the peak transient mean-square response of the system on the damper/inerter tuning parameters, and the shape of the deterministic intensity function. It is shown that, under favorable dynamic environments, a properly designed auxiliary damper, encompassing an inerter with a sizable mass ratio, can significantly attenuate the response of the primary system to broad band excitations; however, the dimensionless “rise-time” of the nonstationary excitation substantially reduces the effectiveness of such a class of devices (even when optimally tuned) in attenuating the peak dynamic response of the primary system.

scholarly journals Charge-to-mass ratio of individual blowing-snow particles

1998 ◽  
Vol 26 ◽  
pp. 207-211 ◽  
Author(s):  
D. S. Schmidt ◽  
J. D. Dent ◽  
R. A. Schmidt
Keyword(s):  
Negative Charge ◽  
Electrostatic Force ◽  
Average Charge ◽  
Blowing Snow ◽  
Mass Ratio ◽  
Mass Ratios ◽  
Snow Storm ◽  
Individual Particles ◽  
Large Charge ◽  
Snow Samples

Determining the electrostatic force acting on saltating snow particles requires knowledge of the electric field in the saltation region and the charge on the particle. To date, measurements of average charge-to-mass ratios for blowing-snow samples have been made but Schmidt and Schmidt (1993) have indicated these may underestimate charge-to-mass ratios for individual particles due to a mixture of positive and negative charge in the samples. This paper reports on measurements of charge-to-mass ratio for individual blowing-snow particles during a moderate blowing-snow storm in southwestern Wyoming. We measured charge-to-mass ratios as large as -208μC,kg-1, significantly higher than the -10μC kg-1measured by Latham and Montagne (1970) and -50μCkg-1measured by Wishart (1970). This large charge-to-mass ratio was accompanied by a distribution of positive and negative charge on the particles, supporting the conclusions of Schmidt and Schmidt (1993).

Tailoring multistable vibrational energy harvesters for enhanced performance: theory and numerical investigation

2019 ◽  
Vol 96 (2) ◽  
pp. 1283-1301 ◽  
Author(s):  
Mickaël Lallart ◽  
Shengxi Zhou ◽  
Linjuan Yan ◽  
Zhichun Yang ◽  
Yu Chen
Keyword(s):  
Numerical Investigation ◽  
Vibrational Energy ◽  
Performance Theory ◽  
Energy Harvesters
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